This project will carefully evaluate the quality of data on age- specific mortality rates at the older ages (e.g., above 40) in approximately twenty-five developed countries since 1950. The evaluation will focus on a comparison of the consistency of census and death registration data for open-ended cohorts (e.g., age 60+) from one census to the next. In most countries, the evaluation will use census and registration data classified by single years of age. The data evaluation will be supplemented by a systematic review of literature on data quality in the countries considered and by direct communication with national statistical agencies. Data that passes our tests of accuracy will be entered into a data set that will be used to construct new model life tables for advanced ages in low mortality countries. No existing set of model life tables incorporates data beyond the 1950s for these countries. In place of such models, age-patterns of mortality at the very old ages are often assumed to follow a Gompertz curve or other mathematical formula. These assumptions have rarely been tested against data of certified accuracy. Model life tables will provide a solid empirical basis for projecting mortality rates and population number at older ages and for extrapolating mortality rates into age intervals for which data accuracy is poor or unknown. They will also provide a useful metric for examining the pace of mortality change at different Ages in specific countries. A by-product of the research will be an estimation of the most likely patterns of age misreporting that have given rise to observed inconsistencies between census and death registration data in various countries. This examination will involve both simulation and statistical estimation of a matrix of age-reporting coefficients.